Killer smart material shrugs off bugs

Philip Ball

About the author

Philip is a writer based in London. He writes on all areas of the sciences and its interactions with art and wider culture. He was previously an editor for the science journal Nature for two decades and is the author of many books on science, including The Self-Made Tapestry: Pattern Formation in Nature, H2O: A Biography of Water, Critical Mass (winner of the 2005 Aventis Prize for Science Books), and The Music Instinct. You can find out more at his website or blog.

Related

Some bacteria can evade efforts to vaccinate against them by wearing a new disguise, researchers say.

Almost by definition, science news dwells on the exceptional: the rare advances that promise (even if they do not succeed) to make a difference to our lives, or our view of the universe. But while it is always fair to confront any research with the question “so what?” and while you can hardly expect everyone to be interested in the mundane or the obscure, the fact is that behind much of what scientists do lies a good, and often extraordinary, story.

Yet unless they happen to stumble upon some big advance (or at least, an advance that can be packaged and sold as such), most of those stories are never told.

These studies languish beneath the forbidding surface of papers published by specialised journals, and you would often never guess from their baffling titles that they have any connection to anything useful, or that they harbour anything to spark the interest of more than half a dozen specialists in the world. This column aims to redress some of the balance by unearthing some of those buried treasures and explaining why they are worth polishing.

One reason why much of the interesting stuff gets overlooked is that good ideas rarely answer all of the important questions at once. Many projects are ignored or passed over because they have not reached the point where they cross a reporter’s ‘significance threshold’, and then when the work finally gets to a useful point, it is deemed unworthy of coverage because much of it has been published already. As a result, science is presented as a succession of breakthroughs, with little indication of the difficulties that lie between fundamental research and viable applications, or between a smart idea and a proof that it is correct.

Bug-killing film

Take a recent report by Shaoyi Jiang – a chemical engineer at the University of Washington in Seattle – and his colleagues in the journal Angewandte Chemie. They have created an antimicrobial polymer coating which can be switched between a state in which it kills bacteria - eliminating 99.9% of sprayed-on E. coli - and one where it shrugs off the dead cells and resists the attachment of new ones. That second trick is a valuable asset for a bug-killing film, since even dead bacteria can trigger inflammation.

They had already achieved this three years ago, but there is a key difference within their latest paper. Before, the switching was a one-shot affair: once the bacteria were killed and removed, you could not get the bactericidal film back. If the bacteria then returned, you would be in trouble.

This is why the researchers continued their labours to make their films fully reversible, which they have achieved with some clever chemistry. They created a polymer layer sporting molecular “hairs” like a carpet, with each hair ending in a ring-shaped molecule that is deadly to bacteria. If the surface is moistened with water, the ring springs open, transformed into a molecular group to which bacteria cannot easily stick. Just add a weak acid – acetic acid, basically vinegar – and the ring snaps closed again, regenerating a bactericidal surface as potent as before.

This work fits with a growing trend to make materials ‘smart’ – able to respond to changes in their environment. There was a time when a single function was all you got: a non-adhesive “anti-fouling” film, say, or one that resists corrosion or reduces light reflection, which is handy for solar cells. But increasingly, we want materials that do different things at different times or under different conditions: for instance, materials that can be switched between transparent and mirrored, or between water-wettable and water-repelling. There is now a host of such protean substances that might be equipped for these tasks.

Another attraction of Jiang’s coating is that these switchable molecular carpets can in principle be coated on to a wide variety of different surfaces, including metal, glass and plastics. The researchers say that it could be used on hospital walls, or on the fabric of military uniforms to combat biological weapons. That sort of promise is generally where journalism stops, and the hard work of turning this neat idea into reliable, safe and affordable mass-produced materials really begins.

If you would like to comment on this story or anything else you have seen on Future, head over to our Facebook page or message us on Twitter.